Process for preparing esters

ABSTRACT

A process for preparing an ester wherein a water soluble organic acid is contacted with a water insoluble alkanol in added water containing a sulfonic acid having from 12 to 20 carbon atoms.

United States Patent Hay et al.

[ 51 Sept. 19, 1972 [54] PROCESS FOR PREPARING ESTERS [72] Inventors: Russell G. Hay, Gibsonia; John G. McNulty; William L. Walsh, both of Glenshaw, all of Pa.

[73] Assignee: Gulf Research 8: Development Company, Pittsburgh, Pa.

[22] Filed: April 20, 1970 [21] Appl. No.: 30,235

[56] References Cited UNITED STATES PATENTS 2,903,477 9/1959 Hughes et a1 ..260/475 B Mohan et a1 ..260/485 Schetelich et a1. ..260/485 Primary Examiner-Lorraine A. Weinberger Assistant Examiner-E. Jane Skelly Attomey-Meyer Neishloss, Deane E. Keith and Joseph J. Carducci 57 ABSTRACT A process for preparing an ester wherein a water soluble organic acid is contacted with a water insoluble alkanol in added water containing a sulfonic acid having from 12 to 20 carbon atoms.

13 Claims, No Drawings PROCESS FOR PREPARING ESTERS This invention relates to a process for preparing esters.

When an organic acid is reacted with an alkanol in conventional procedures to produce the corresponding ester, water is formed as a by-product, which must be removed continuously from the reaction zone for the desired reaction to continue. We have found that water need not be removed during the esterification reaction provided the reaction is carried out in the presence of added water and a selected amount of a sulfonic acid having from 12 to 20 carbon atoms. In this way distillation'equipment is not needed during the reaction and a desirable saving is thereby obtained.

The water soluble organic acid used herein can be either monobasic or dibasic. Monobasic acids that can be used will have from two to four carbon atoms, preferably from two to three carbon atoms, while the dibasic acids will have from four to 20 carbon atoms, preferably from four to carbon atoms. Specific examples of monobasic acids that can be used are acetic, propionic, butyric and isobutyric acids. Examples of dibasic acids that can be employed include specific examples of aliphatic straight and branched dibasic acids, such as succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, methylsuccinic acid, dimethylsuccinic acid, methyladipic acid, etc; specific examples of straight and branched olefinic dibasic acids, such as maleic acid, fumaric acid, methylmaleic acid, dimethylmaleic acid, ethylmaleic acid, methylfumaric acid, dimethylfumaric acid, chloromaleic acid, dichloromaleic acid, glutaconic acid, etc.; specific examples of cyclic dibasic acids, such as cyclohexane dicarboxylic acid, cyclopentane dicarboxylic acid, cyclododecane dicarboxylic acid, etc.; specific examples of aromatic dibasic acids, such as ortho-phthalic acid, nitrophthalic acid, tetrachlorophthalic acid, etc. and specific examples of polybasic acids, such as tricarballylic acid, aconitic acid, citric acid, etc. Since anhydrides corresponding to the above dibasic acids will be converted to dibasic acids in the reaction system it is apparent that the corresponding anhydrides can also be employed her-rein.

The water-insoluble alkanols that are reacted with the organic acids defined above are water-insoluble alkanols having from five to 16 carbon atoms, preferably from six to 12 carbon atoms. Specific examples of such alkanols are 3-methylbutanol-l, normal amyl alcohol, normal hexyl alcohol, normal heptyl alcohol, 2-ethylhexanol-l, 3-methylhexanol-l, normal octyl alcohol, 2- methylheptanol-l, 3-methylheptanol-l, normal nonyl alcohol, 2-methyloctanol-l, normal decyl alcohol, 2- methylnonanol-l, normal unidecyl alcohol, normal dodecyl alcohol, 2-methyldecanol-l, normal hexadecyl alcohol,etc. H 7 V n V 7 H The amounts of alkanols needed in the esterification reaction defined herein can be varied over wide limits. Although theoretically one mol of alkanol is required for each acid function on the organic acid, in general the molar ratio of alkanol per mol of acid function can be from about 1:10 to about 10:1, preferably from about 1:5 to about 5: 1.

As noted, not only is the water of reaction not removed during the course of the reaction defined herein, but additional water is added to the reaction zone. The molar ratio of water added per mol of alkanol is from about 1:1 to about :1, preferablyfro m about 2: l to about 40:1.

Also needed in the reaction zone is a sulfonic acid having from 12 to 20 carbon atoms, preferably from [2 to 18 carbon atoms. Specific examples of sulfonic acids that can be employed are normal decylbenzenesulfonic acid, normal dodecylbenzene sulfonic acid, normal nonylbenzenesulfonic acid, normal octylbenzenesulfonic acid, normal heptylbenzenesulfonic acid, normal hexylbenzenesulfonic acid, normal tridecylsulfonic acid, normal tetradecylbenzenesulfonic acid, normal dodecanesulfonic acid, normal tridecanesulfonic acid, normal tetradecanesulfonic acid, normal pentadecanesulfonic acid, normal hexadecane sulfonic acid, normal heptadecanesulfonic acid, normal octadecanesulfonic acid, normal nonadecanesulfonic acid, normal eicosanesulfonic acid, 3-methyldodecanesulfonic acid, 3-methyl-5-ethyldecanesulfonic acid, 3-methyldecylbenzenesulfonic acid, 4- ethyloctylbenzenesulfonic acid, etc. By normal" we mean linear. The amount of sulfonic acid required is at least about 0.05 per cent by weight based upon the total reaction mixture, preferably from about 0.2 to about 2 per cent by weight.

The reaction is simply effected. All that need be done is to bring the reactants together in water containing the defined sulfonic acid at an elevated temperature, for example, from about C. to about 250 C., preferably about C. to about 200 C., for about one minute to about 40 hours, preferably for about 15 minutes to about three hours. Pressure is not critical and is dependent upon the vapor pressure of water at reaction temperature. Thus, a pressure of about 100 to about pounds per square inch gauge, preferably about 100 to about 115 pounds per square inch gauge can be used.

The product ester can be recovered from the reaction product in any convenient manner. At the end of the reaction period, for example, the reaction product resolves itself into an upper organic layer and a lower aqueous layer, which can be separated from each other in any convenient manner, for example, by decantation. Distillation of the organic layer will separate the various components thereof, including the desired ester, from each other.

The process defined herein can further be illustrated by the following. Several runs were carried out in closed glass reactor having a volume of 300 milliliters, wherein various materials were brought together and heated at an elevated temperature for a designated period of time and a pressure of about 1 10 to about 1 15 pounds per square inch gauge. The contents of the reactor were then cooled to room temperature and analyzed by gas chromatography. The results obtained are tabulated in TABLE I.

TABLE 1 '7 Grams of additive Mols charged Para Normal Weight toluenedodecylpercent of Ortho sulbenzenedioctyl phthalic ionic sulfonic Temp, Time, phthalate Run N o Octanol-l acid Water acid acid C. hours in product The uniqueness of the process defined herein is apparent from the above. Note that when octanol-l was reacted with ortho phthalic acid and water of reaction was not permitted to leave the reaction zone 25.4 per cent of the reaction product was dioctyl phthalate In Run No. 2 when added water was also present the weight per cent of ester was reduced to 7.9. The addition of 0.70 gram of para toluenesulfonic acid, a well known esterification catalyst, to the system in Run No. 3 failed to increase the amount of desired ester. A comparison of Run No. 4 with Run No. 2 shows that the addition of a small amount of a sulfonic acidwithin the scope of the present process to a system containing organic acid, alkanol and added water resulted in a substantial increase of ester. In Run No. 5 an efiort was made to increase the amount of ester produced in a system similar to that of Run No. 4 by the addition thereto of an esterification catalyst. Although some improvement seems to have been noted we believe no real improvement can be alleged, and that the small difference observed may be due solely to experimental error.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for preparing an ester which comprises contacting a water soluble organic acid selected from the group consisting of monobasic hydrocarbon carboxylic acids having one to four carbon atorns and dibasic hydrocarbon carboxylic acids having from four to 20 carbon atoms with a water insoluble alkanol having five to 16 carbon atoms in added water containing a monoalkyl benzene sulfonic acid having from 12 to 20 carbon atoms.

2. The process of claim 1 wherein the organic acid is a monobasic hydrocarbon carboxylic acid.

3. The process of claim 1 wherein the organic acid is a dibasic hydrocarbon carboxylic acid.

4. The process of claim 1 wherein the organic acid is a phthalic acid.

5. The process of claim 1 wherein the organic acid is ortho phthalic acid.

6. The process of claim 1 wherein the alkanol is octanol-l.

7. The process of claim 1 wherein the sulfonic acid is dodecylbenzenesulfonic acid.

8. The process of claim 1 wherein the amount of sulfonic acid present is at least about 0.05 per cent by weight based upon the total reaction mixture.

9. The process of claim 1 wherein the amount of sulfonic acid present is from about 0.2 to about two per cent b weight based on the total reaction mixture.

0. e process of claim 1 w erein the molar ratio of added water to alkanol is from about 1:1 to about :1.

1 1. The process of claim 1 wherein the molar ratio of added water to alkanol is from about 2:1 to about 40:1

12. The process of claim 1 wherein the reaction is carried out in a temperature range of about C. to about 250 C.

13. The process of claim 1 wherein the reaction is carried out in a temperature range of about C. to about 200 C. 

2. The process of claim 1 wherein the organic acid is a monobasic hydrocarbon carboxylic acid.
 3. The process of claim 1 wherein the organic acid is a dibasic hydrocarbon carboxylic acid.
 4. The process of claim 1 wherein the organic acid is a phthalic acid.
 5. The process of claim 1 wherein the organic acid is ortho phthalic acid.
 6. The process of claim 1 wherein the alkanol is octanol-1.
 7. The process of claim 1 wherein the sulfonic acid is dodecylbenzenesulfonic acid.
 8. The process of claim 1 wherein the amount of sulfonic acid present is at least about 0.05 per cent by weight based upon the total reaction mixture.
 9. The process of claim 1 wherein the amount of sulfonic acid present is from about 0.2 to about two per cent by weight based on the total reaction mixture.
 10. The process of claim 1 wherein the molar ratio of added water to alkanol is from about 1:1 to about 80:1.
 11. The process of claim 1 wherein the molar ratio of added water to alkanol is from about 2:1 to about 40:1.
 12. The process of claim 1 wherein the reaction is carried out in a temperature range of about 100* C. to about 250* C.
 13. The process of claim 1 wherein the reaction is carried out in a temperature range of about 120* C. to about 200* C. 